Colloquium Detail

Measurement of Cosmological Parameters via Gravitational Lensing

Date:
11/16/2000

Charles Baltay
Professor, Yale

Quasars are the furthest objects visible in the universe: they
can be seen at truly cosmological distances of billions of light years
away. Gravitational lensing occurs when an intermediate large mass
(the lens) distorts the quasar image into multiple images. This allows
us to look for dark matter as invisible lenses and to measure Hubbles
constant without the uncertainties of the infamous "Distance Ladder".
The geometry and probability of a lensing event provides a measurement
of the geometry of space-time that is then sensitive to the cosmological
parameters such as the mass density, the cosmological constant, and
possibly the equation of state of "Dark Energy" required by an
accelerating expansion of the universe.